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Nightshade vegetables, which include potatoes and tomatoes, are common foods with a lot of nutrients. Some believe, however, that they can trigger inflammation and immune dysfunction.

Nightshade vegetables belong to the family of plants with the Latin name Solanaceae.

Potatoes, tomatoes, peppers, and eggplants are all common nightshades. Many are rich sources of nutrients and serve as staple foods for various cultures.

However, some believe that certain groups of people may be better off eliminating nightshades. They claim that harmful substances found in these vegetables may contribute to inflammatory bowel disease and other autoimmune conditions.

This article reviews the health effects of nightshade vegetables to help you decide if these foods are right for you.

What are nightshade vegetables?

Nightshade vegetables are the edible parts of flowering plants that belong to the Solanaceae family.

The origin of the name nightshades is unclear, but could be related to their dark and mystical past. Some nightshades are rumored to have been formerly used as narcotics and hallucinogens.

The nightshade family contains over 2,000 varieties of plants, but very few of them are actually eaten as food. Some, such as belladonna, are even poisonous.

However, nightshades also include vegetables that have been staple foods of many societies for hundreds of years.

Some of the most commonly consumed nightshade vegetables include:

• eggplants
• peppers
• potatoes
• tobacco
• tomatillos
• tomatoes

Multiple herbs and spices are also derived from these vegetables, including cayenne pepper, crushed red pepper, chili powder, and paprika.

Black and white pepper are derived from peppercorns, which are not in the nightshade family.

Additionally, several condiments and other common food items contain nightshade vegetables as ingredients, such as hot sauce, ketchup, marinara sauce, and salsa.

Although they’re generally referred to as vegetables, many nightshades are botanically considered fruits, such as tomatoes, eggplants, and peppers.

Nightshades belong to the Solanacaea family of plants. They include potatoes, tomatoes, eggplants, and peppers.

Rich sources of nutrients

Many health professionals encourage you to eat nightshades because of their high nutrient density.

This means they pack a lot of nutrients with fewer calories.

• Tomatoes: Tomatoes are good sources of vitamins A and C. They also contain an antioxidant called lycopene. These nutrients may reduce markers of inflammation and lower the risk of several chronic diseases (1, 2).
• Peppers: Peppers contain incredible amounts of vitamin C, which can provide many health benefits, including helping enhance iron absorption (3).
• Chili peppers: Chili peppers contain capsaicin, which gives the peppers their heat. Supplementing with capsaicin powder has been found to help alleviate heartburn symptoms and may benefit weight loss efforts by helping reduce calorie intake (4, 5).
• Eggplants: Eggplants are a good source of dietary fiber, providing 2.5 grams of fiber per cup. This important nutrient helps regulate bowel movements and may lower your risk of heart disease (6).
• Potatoes: Potatoes with the skins on contain fair amounts of potassium, vitamin B6, and manganese (7).

However, unlike most nightshades, potatoes are a starchy vegetable. One small potato contains around 30 grams of carbs (7).

People with diabetes or others looking to lower their blood sugar may need to avoid eating too many potatoes.

Nightshades are nutrient-dense foods that may provide a number of health benefits through their vitamin, mineral, fiber, and antioxidant content.

Are they harmful for people with autoimmune diseases?

Although nightshade vegetables are a rich source of nutrients, many people claim they’re harmful and should be avoided.

The majority of these claims seem to center around a group of substances found in nightshades called alkaloids.

Alkaloids are nitrogen-containing substances typically found in the leaves and stems of nightshades. They’re often very bitter and function as a natural insect repellent.

But the edible portions of these plants contain some alkaloids, too. Consequently, many people with autoimmune diseases eliminate nightshades from their diets, believing they contribute to their health problems.

However, research has yet to show that nightshade vegetables contribute to autoimmune diseases.

Inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of autoimmune diseases characterized by inflammation of the digestive tract. Examples are Crohn’s disease and ulcerative colitis.

In people with IBD, the protective lining of the intestine doesn’t function properly and allows bacteria and other harmful substances to enter the bloodstream (8, 9).

This is sometimes called increased intestinal permeability, or “leaky gut” (10).

When this happens, the body’s immune system attacks the harmful substances, leading to further inflammation of the gut and many adverse gastrointestinal symptoms, such as pain, diarrhea, and malabsorption.

While research on this is limited, a few studies in animals suggest that the alkaloids in nightshades may further aggravate the intestinal lining of people with IBD.

In two separate studies on mice with IBD, the alkaloids in potatoes were found to adversely affect intestinal permeability and increase intestinal inflammation (11, 12).

It’s important to note that the alkaloids in these studies were in far higher concentrations than the amount found in a normal serving.

Additionally, two test-tube studies suggest that chemicals called lectins in tomatoes and capsaicin in peppers may also increase intestinal permeability (13, 14).

This limited research in animals and test tubes suggests that people with IBD may benefit from eliminating or reducing nightshades. But research is needed in humans before more definitive recommendations can be made.

Effects on other autoimmune diseases

Even less is known about the effects of nightshades on other autoimmune diseases.

However, there may be some connection between increased intestinal permeability, or leaky gut, and autoimmune conditions like celiac disease, multiple sclerosis, and rheumatoid arthritis (15, 16).

Some experts believe that leaky gut could contribute to higher levels of inflammation all over the body that worsen disease symptoms (17, 18).

Based on this belief, some have suggested that nightshades may increase intestinal permeability and aggravate the symptoms of these autoimmune conditions, as well.

Many people with these diseases have eliminated nightshades from their diets and report improvement in symptoms, but evidence for this recommendation right now is mainly anecdotal and needs to be studied.

Some animal studies suggest that nightshades could have negative effects in people with IBD, but more research is needed in humans before recommendations to eliminate nightshades can be made.

Sensitivities and allergies

Other groups of people without autoimmune conditions claim that eliminating nightshades has dramatically improved their health.

These people are often said to have sensitivities to nightshades.

One of these groups includes people with arthritis, as some claim that eliminating nightshades provides pain relief.

There’s an older theory that nightshades contain a form of vitamin D that causes calcium deposits that may contribute to joint pain and other arthritis symptoms.

It is true that a vitamin D-like substance was discovered in plants in the nightshade family. And some studies have reported that animals feeding on these plants have developed calcium deposits in soft tissues, which cause health problems (19, 20, 21).

However, there doesn’t appear to be evidence that nightshades contain vitamin D or that eating these vegetables causes calcium deposits, arthritis symptoms, or other related health problems in humans.

In addition to nightshade sensitivities, in rare cases, some people have allergies to specific nightshade vegetables.

Symptoms of an allergy vary but can include skin rashes, hives, itching in the throat, swelling, and difficulty breathing (22, 23).

If you experience any of these symptoms when you eat a particular nightshade vegetable, it would be wise to stop eating that particular food and seek medical advice for further testing.

If you want to start an elimination diet, reach out to a doctor or dietitian.

People claiming to have nightshade sensitivities have found symptom relief by avoiding them, though there’s no research supporting this. Others have rare allergies to nightshades.

Eliminating nightshades

If you’re healthy and don’t have adverse reactions to nightshades, there’s no compelling reason to avoid them.

They’re rich in nutrients and offer several potential health benefits.

On the other hand, if you have an autoimmune condition like IBD or think you may be sensitive to nightshades, you might want to consider removing them from your diet to evaluate changes in symptoms.

If you decide to do this, completely eliminate all nightshades and products containing these vegetables for at least 4 weeks. Be sure to keep track of the severity of your symptoms during this time.

After this elimination period, you should start reintroducing nightshade vegetables one at a time back into your diet. Don’t make any other lifestyle changes during this time.

After reintroducing nightshades, compare the severity of your symptoms during your elimination and reintroduction periods.

If symptoms were better during elimination and got worse when you reintroduced nightshades, you may want to continue to avoid eating them long-term.

If symptoms weren’t different between the two periods, you should seek other treatments for your symptoms and continue eating nightshades.

Most people are encouraged to eat nightshade vegetables. However, if you have an autoimmune condition, you may consider eliminating nightshades to evaluate any changes in symptoms.

Substitutes for common nightshade vegetables

If you decide to eliminate nightshades long-term, you’ll be missing out on the nutrients they provide.

However, there are plenty of other foods to choose from that provide many of the same nutrients and health benefits.

Here are a few changes you can make to eat healthy while avoiding nightshades:

• Switch to sweet potatoes. Switching from white potatoes to sweet potatoes will help you avoid nightshades and provide much more vitamin A.
• Use pesto. Instead of tomato sauce in pizza and pasta, green pesto is a delicious alternative that should not contain nightshades. Red pesto usually contains tomatoes and should be avoided if trying to eliminate nightshades.
• Consume citrus fruits. Many nightshadess contain vitamin C, but citrus fruits like oranges, tangerines, and grapefruits are also excellent sources.
• Eat more leafy greens. Leafy green vegetables like spinach, kale, and collard greens are great sources of many vitamins, minerals, and dietary fiber.

If you still want to eat nightshades but would like to lower their alkaloid content, you can accomplish this by peeling your potatoes, limiting green tomatoes, and fully cooking these vegetables.

Eliminating nightshades means missing out on some important nutrients. However, there are many other nutrient-rich foods you can try.

The bottom line

Nightshade vegetables contain important nutrients and provide many health benefits. Most people are encouraged to eat them.

Other people may choose to avoid nightshades due to sensitivities.

If you feel that you’re sensitive to nightshades, there are plenty of other fruits and vegetables you can eat instead as part of a healthy diet.